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  1. Onemorechance

    Effect of winglets on ground effect

    I would think that if the winglets point down, the induced drag would be smaller because the vortex leaving the wing at the winglet is closer to and better neutralized by it's image in the ground. On the other hand, if the winglets point upward, then the opposite is true, the vortex leaving the...
  2. Onemorechance

    Propeller efficiency versus efficiency losses.

    Yes, it only depends on how you define it. If defined as follows: Overall Propeller Efficiency = Useful Power / PowerIn = (Useful Power / PowerOut)* (PowerOut / PowerIn) Then an ideal propeller has efficiency < 100%, because Useful Power < PowerOut. (Useful power is the Thrust * Airspeed)
  3. Onemorechance

    Propeller efficiency versus efficiency losses.

    When you say that a propeller has an efficiency of 51%, does it then mean that the efficiency losses with respect to the ideal propeller are 49%? My answer would be NO! Why? Because the ideal propeller will have an efficiency lower than 100%! Therefore the losses with respect to the ideal...
  4. Onemorechance

    Ducted Fan

    OK GregLocock I was a bit fast with my assumption of 10% losses. Realizing now that the fan has lots of blades, I must admit that the efficiency will be lower compared to a propeller with the same diameter and much less blades. Sorry.
  5. Onemorechance

    Ducted Fan

    I’m sure the US Army does more than just fly around and shoot down enemies with AH-64 Apache Helicopters. Also when I am saying that I like it, I really mean that I like it when people are trying to invent and make new things work. They may not be perfect and in desperate need of improvement...
  6. Onemorechance

    Passive Torque Control

    Sorry for answering so late, I don't have too much time for this. Do you mean to shape the fuselage as a vertical wing over the whole diameter of the rotor, from back to front? Anyway, there are more options also. I am not kidding; one option could be for example to drive the rotors not by...
  7. Onemorechance

    Passive Torque Control

    Whoops, its even worse because I made a mistake in equation (4). should be v = Sqrt(W / (0.5 * ? * Pi * d^2)), so (5) becomes: c = 2 * Sqrt(32 * Pi * W / ?) / (cl * d * Rot) in the example the chord c would become almost (5m) the same as the span d/2 (5m) of the wing!
  8. Onemorechance

    Passive Torque Control

    Hi Dallasrotor, Once, I also played with the idea of using a wing-like tail-boom in the down wash to counter torque. My conclusion at the time was that the surface area needed to be too high to be practical and that the rotation in the down wash even increased the already high "induced drag"...
  9. Onemorechance

    dimples

    Look at this: maybe you'll learn what you need: Some more on dimple aerodynamics
  10. Onemorechance

    dimples

    Well, I forgot to tell, I do have a formula (but incomplete because you still need a cd-value). Once you have a cd-value for the wheel with dimple that you want to study, you can find the total drag with the following formula: Drag = cd * S * .5 * ? * V^2 S = wheel reference area ? = air...
  11. Onemorechance

    dimples

    Yes a turbulent boundary layer creates more friction-drag than a laminar one. But the drag of the wheel (same for a wing) is not only due to the friction in the boundary layer, but also of PRESSURE-drag caused by the pressure distribution in the flow-field outside the boundary layer. A turbulent...
  12. Onemorechance

    dimples

    Dimples work like vortex generators on a wing. They cause the boundary layer to become turbulent and therefore enable it to stay better attached to the wheel. Overall they will reduce the aerodynamic drag of the wheel.
  13. Onemorechance

    Ducted Fan

    2 feet is a bit exaggerated, when you see him standing in profile he leans a bit forward, I 'd say a few inches. Seems to me that, or the thing is actively stabilized, or you 'll need weeks of practice to learn how to fly it because it can not be naturally stable. Also a landing with more than...
  14. Onemorechance

    Wing spar stress calculations

    Karlbamforth, Don’t loose courage. You will never have a perfect loads (lift and torque) distribution over your wing and canard, that is true, but you can take a conservative approach. The wing sweep will increase the cl(y) distribution towards the tips and lower it towards the middle, same...
  15. Onemorechance

    One prop governor for two propellers

    Instead of a syncrophaser, I think I have an easier solution: When connecting the high-pressure governor line between the left and right propeller with a ball check valve, the problem can be solved (I think). By doing so, the difference in pressure between left and right can be equalized during...
  16. Onemorechance

    One prop governor for two propellers

    Let me try show you the possibilities: 1. One governor on the engine Left Propeller __________| |__________ | |_____________ | ____________ | | | |...
  17. Onemorechance

    One prop governor for two propellers

    Well Steven and Mike, First thank you for your reply. It is a preliminary study that we are doing. There are several reasons why we chose to have this engine and the 2 props. I don't want to explain all about it except that this small aircraft is supposed to have besides conventional TOL, also...
  18. Onemorechance

    One prop governor for two propellers

    I don't know if I can describe it in detail, but the problem is basically as follows: We have a gas turbine engine (420 shp turboshaft engine mostly used in helicopters). We want to use it in an experimental aircraft. The engine would drive 2 counter rotating constant speed propellers (probably...
  19. Onemorechance

    Wing spar stress calculations

    karlbamforth, What kind of wing beam do you have? You could have a single closed wing box with front and rear spars. You could also have a wing box made up by most (or part) of the wing with several webs forming a multiple closed cells beam. In the case you have distinct spars, these could be...
  20. Onemorechance

    Engine locations

    Sorry, Less chances of ingestion of debris from the runway during Take Off Should be in the Advantages-list. OneMoreChance

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